Fishing For AirPods With Magnets

July 30, 2017 by Dan Maloney 35 Comments

Note to self: if you’re going to hack at 4 in the morning, have a plan to deal with the inevitable foul ups. Like being able to whip up an impromptu electromagnetic crane to retrieve an AirPod dropped out a window.

Apartment dweller [Tyler Efird]’s tale of woe began with a wee-hours 3D print in need of sanding. Leaning out his third-story window to blow off some dust, he knocked one AirPod free and gravity did the rest. With little light to search by and a flight to catch, the wayward AirPod sat at the bottom of a 10-foot shaft below his window, keeping company with a squad of spiders for two weeks. Unwilling to fork over $69 and wait a month and a half for a replacement, [Tyler] set about building a recovery device. A little magnet wire wound onto a bolt, a trashed 100-foot long Ethernet cable, and a DC bench supply were all he needed to eventually fish up the AirPod. And no spiders were harmed in the making of this hack.

Need to lift something a little heavier than an AirPod? A beefy microwave oven transformer electromagnet might be the thing for you. And confused about how magnets even work in the first place? Check out our primer on magnetism.

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How To Levitate 100lbs

February 1, 2017 by Cameron Coward 22 Comments

Most of our readers are already going to be familiar with how electromagnets work — a current is induced (usually with a coil) in a ferrous core, and that current aligns the magnetic domains present in the core. Normally those domains are aligned randomly in such a way that no cumulative force is generated. But, when the electric field created by the coil aligns them a net force is created, and the core becomes a magnet.

As you’d expect, this is an extremely useful concept, and electromagnets are used in everything from electric motors, to particle accelerators, to Beats by Dre headphones. Another use that you’re probably familiar with from your high school physics class is levitation. When two magnets are oriented with the same pole towards each other, they repel instead of attract. The same principle applies to electromagnets, so that an object can be levitated using good ol’ electricity.

That, however, isn’t the only way to levitate something using magnets. As shown in the video below, permanent magnets can be used to induce a current in conductive material, which in turn exerts a magnetic field. The permanent magnets induce that current simply by moving — in this case on rotors spun by electric motors. If the conductive material is placed below the magnets (like in the video), it will push back and you’ve got levitation.

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Heavy Lift Electromagnet From Microwave Oven Transformers

January 15, 2017 by Dan Maloney 41 Comments

It’s OK, you can admit it — from the time you first saw those huge electromagnetic cranes in scrap yards you’ve wanted to have one. While it may not fling around a car, parts donated from scrapped microwaves can let you build your own electromagnetic lifting device and make that dream finally come true.

We recently watched [MakeItExtreme] turn a couple of microwave oven transformers into a somewhat ill-advised wall-climbing rig. It looks like that may have been the inspiration for this build, and the finished product appears to be a tad more useful this time. The frames of three MOTs are cut open to remove the secondary coils and leave the cores exposed as poles for the future magnets. A shallow dish is fabricated out of steel and the magnets are welded in place.

With the primaries wired together, the magnets are epoxy potted, the business end is faced off cleanly, and the whole thing put to the test. [MakeItExtreme] doesn’t go into control details in the video below, but the website mentions the magnet being powered off a 24V 15A power supply with battery backup in case of mains failure.

They’ve lifted 200kg so far, and it looks like a pretty cool addition to a shop already packed with other builds, like their MOT spot welder and a propane tank sandblaster.

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Microwave Ovens Turn You Into Spiderman

October 14, 2016 by Dan Maloney 43 Comments

Want to climb a wall like Spiderman? No problem – just whip up a climbing rig with microwave oven transformers. And find a steel building. And rewrite the canon so that Peter Parker is bitten by an electromagnetic spider instead of a radioactive one.

Back in the reality-based world, you’d probably be taking you life in your hands if you use [Make It Extreme]’s rig to get more than a dozen feet above the ground. The basics are pretty sound, but the devil is in the details. Four MOTs are cut and stripped of their secondary coils and attached to fixtures for the feet and hands. A backpack full of gel cell batteries powers the rig, and simple normally closed switches in the handholds control both the foot and hand magnets on a side. A click of a switch releases the magnets on one side, allowing the climber to reach up.

And therein lies our safety beef: what happens when you make a mistake and push both buttons at the same time? Seems like this build is screaming for some control circuitry that prevents this most obvious failure mode. We’re not ones to throw an Arduino at every problem, but in this case it may make sense, especially when it could monitor ~~your time left before cratering~~ the charge remaining in the battery pack.

Still, like most dangerous stunts, this looks really cool. If you’ve got any ideas for improvements in the controls, leave them in the comments below. And if you’re interested in transforming yourself into a superhero, learn from a guy who’s actually doing it – our own [James Hobson]. Check out some of his builds, like the Captain America shield or his car-lifting exoskeleton.

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Shoot Hard Drive Platters Skywards On The Power Of Magnetism

March 10, 2016 by Jenny List 35 Comments

Project Hathor is an electromagnetic ring launcher that launches aluminium hard drive platters 45 feet skywards at the touch of a button. The hard work is done by a bank of capacitors which are charged to 2kV from a microwave oven transformer, before being discharged into a coil of wire on which the hard drive platter is sitting. The resulting burst of magnetic field induces a huge current in the platter, and that current in turn creates an opposing field which launches the ring into the air.

The launcher is the work of [Krux], at the Syn Shop hackerspace in Las Vegas, and he’s made a beautiful job of it. The capacitor bank has ten 3900uF 400V electrolytic capacitors wired as a single 1560uF 2kV capacitor, there are two 225W 2Kohm wire wound discharge resistors, and a beautifully designed home-made high voltage contactor featuring tungsten electrodes. The whole project has been carefully built into an acrylic case for safety, for as [Krux] points out, microwave oven transformers will kill you.

As well as the project web site, there is a YouTube playlist, an image gallery, and a GitHub repository containing all the project’s details. You can see the launcher in action in the video below, launching platters into the Nevada night right on cue.

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Magnetic Levitation With Arduino

November 2, 2015 by Will Sweatman 7 Comments

Getting a magnetic field to balance on another magnetic field is about as easy as balancing a bowling ball on the tip of an ink pen. With a little help from an Arduino mega, however, [EmmaSong] was able to balance a high density neodymium magnet in midair. He pulled off this tricky project using a set of four coils he got off of Taobao (the Chinese version of eBay), a hall effect sensor, and a handful of current regulation ICs.

The coils can be made in house if necessary, with each winding getting about 800 turns of enameled wire. The rest of the circuit is straightforward. It appears he uses a potentiometer for a rough regulation of the current going to the coils, doing the fine tuning in the code which can be found here (.RAR direct download).

We’ve seen magnetic levitation here before, and this project adds to the list of successful techniques to accomplish this difficult project.

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Thor’s Hammer Build Recognizes Its Master’s Hand

October 14, 2015 by Mike Szczys 52 Comments

Only those who have completely insulated themselves from modern pop culture will miss the meaning of a Mjolnir build. It is, of course, the mythical hammer wielded by Thor, and only Thor. It’s a question of being worthy; a question solved perfectly by this electromagnetic Mjolnir build.

Using an electromagnet is smart, right? Just plunk the thing down on something metal (that is itself super-heavy or well-anchored) and nobody will be able to pick it up. It starts to get more interesting when you add a fingerprint reader, allowing only Mjolnir’s Master to retrieve it from atop a manhole cover.

But for us the real genius in the build is that the hammer isn’t burning power from the four 12V batteries most of the time. All of the people in the video below could have picked up the hammer had they first nudged it off the metal plate with their foot. The build uses a capacitive touch-sensor to enable and disable the microwave over transformer used as the electromagnet. An engineering trick like this really separates the gods from the posers.

We hate to admit it, but this is probably a cooler build than the Telsa-Coil powered Mjolin that [Caleb] built a few years back. Still, his held up as the best for many years, and if you’re going to be displaced this really is a build worthy of the new title: coolest Mjolnir hack.

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